yes blog comment is very important for seo and I think Google love blog comment and get more backlink
Good and meaningful Blog Commenting is a healthy activity as it helps you build relationships and also provides opportunities for getting backlinks. If you are a regular features at some good blogs, then you are a known person with respect to the circle or readership of that blog in that field. You can develop good contacts with other people and the blog owner and authors as well. After building good relations, you can offer them guest posting with a link back to your own site. This is of course one aspect of blog comment posting.